I was surprised to find no difference in fuel mileage between the cheap ethanol based Husky 87 or Shell 87 vs Chevron 94 octane.

I read on one of the many threads, that someone got a lot more mileage running on high octane gas. So I ran a few tanks of 94 octane at high, high prices and was surprised to find literally no difference in mileage or performance. In the end, it is a "fuel good thing" (pardon the pun). My Micra has 26,000km on it. I'll try again when I have 100K and see if there is any reportable difference.